SCO PALAEONTOLOGY AND EVOLUTION xi 



ankylosed with the tibia. There are three toes 

 on the hind foot having similar proportions to 

 those on the fore foot. The principal metacarpal 

 and metatarsal bones are flatter than they are in 

 any of the Equidce ; and the inetacarpal bones are 

 longer than the metatarsals, as in the Paloecthcria. 



In its general form, PlagiolopJius resembles a 

 very small and slender horse, 1 and is totally unlike 

 the reluctant, pig-like creature depicted in Cuvier's 

 restoration of his Palceotherium minus in the 

 " Ossemens Fossiles." 



It would be hazardous to say that PlagiolopTuu 

 is the exact radical form of the Equine quadru- 

 peds; but I do not think there can be any 

 reasonable doubt that the latter animals have 

 resulted from the modification of some quadruped 

 similar to Plagiolophus. 



We have thus arrived at the Middle Eocene 

 formation, and yet have traced back the Horses 

 only to a three-toed stock ; but these three-toed 

 forms, no less than the Equine quadrupeds them- 

 selves, present rudiments of the two other toes 

 which appertain to what I have termed the 

 " average " quadruped. If the expectation raised 

 by the splints of the Horses that, in some ancestor 

 of the Horses, these splints would be found to 

 be complete digits, has been verified, we are fur- 



1 Such, at least, is the conclusion suggested by the proportions 

 of the skeleton figured by Cuvier and De Blainville ; but per- 

 haps something between a Horse and an Agouti would be nearest 

 the mark. 



